This inexpensive set of gauges eliminates the guesswork when reading the tumblers on 6-cut single-sided GM keys. There is no need to take apart the lock plug or waste key blanks by "eye-balling" the depths. Simply press inward on the side bar and rake the tumblers, until the side bar moves inward to the unlocked position. Then, beginning with the longest gauge, place the gauge pin over each wafer until the shoulder stop butts against the top of the plug.
